/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_rfft_q31.c
*
* Description:	RFFT & RIFFT Q31 process function
*
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/*--------------------------------------------------------------------
*		Internal functions prototypes
--------------------------------------------------------------------*/

void arm_split_rfft_q31(
    q31_t* pSrc,
    uint32_t fftLen,
    q31_t* pATable,
    q31_t* pBTable,
    q31_t* pDst,
    uint32_t modifier);

void arm_split_rifft_q31(
    q31_t* pSrc,
    uint32_t fftLen,
    q31_t* pATable,
    q31_t* pBTable,
    q31_t* pDst,
    uint32_t modifier);

/**
 * @addtogroup RFFT_RIFFT
 * @{
 */

/**
 * @brief Processing function for the Q31 RFFT/RIFFT.
 * @param[in]  *S    points to an instance of the Q31 RFFT/RIFFT structure.
 * @param[in]  *pSrc points to the input buffer.
 * @param[out] *pDst points to the output buffer.
 * @return none.
 *
 * \par Input an output formats:
 * \par
 * Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.
 * Hence the output format is different for different RFFT sizes.
 * The input and output formats for different RFFT sizes and number of bits to upscale are mentioned in the tables below for RFFT and RIFFT:
 * \par
 * \image html RFFTQ31.gif "Input and Output Formats for Q31 RFFT"
 *
 * \par
 * \image html RIFFTQ31.gif "Input and Output Formats for Q31 RIFFT"
 */

void arm_rfft_q31(
    const arm_rfft_instance_q31* S,
    q31_t* pSrc,
    q31_t* pDst)
{
	const arm_cfft_radix4_instance_q31* S_CFFT = S->pCfft;

	/* Calculation of RIFFT of input */
	if(S->ifftFlagR == 1u) {
		/*  Real IFFT core process */
		arm_split_rifft_q31(pSrc, S->fftLenBy2, S->pTwiddleAReal,
		                    S->pTwiddleBReal, pDst, S->twidCoefRModifier);

		/* Complex readix-4 IFFT process */
		arm_radix4_butterfly_inverse_q31(pDst, S_CFFT->fftLen,
		                                 S_CFFT->pTwiddle,
		                                 S_CFFT->twidCoefModifier);

		/* Bit reversal process */
		if(S->bitReverseFlagR == 1u) {
			arm_bitreversal_q31(pDst, S_CFFT->fftLen,
			                    S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
		}
	} else {
		/* Calculation of RFFT of input */

		/* Complex readix-4 FFT process */
		arm_radix4_butterfly_q31(pSrc, S_CFFT->fftLen,
		                         S_CFFT->pTwiddle, S_CFFT->twidCoefModifier);

		/* Bit reversal process */
		if(S->bitReverseFlagR == 1u) {
			arm_bitreversal_q31(pSrc, S_CFFT->fftLen,
			                    S_CFFT->bitRevFactor, S_CFFT->pBitRevTable);
		}

		/*  Real FFT core process */
		arm_split_rfft_q31(pSrc, S->fftLenBy2, S->pTwiddleAReal,
		                   S->pTwiddleBReal, pDst, S->twidCoefRModifier);
	}

}


/**
 * @} end of RFFT_RIFFT group
 */

/**
 * @brief  Core Real FFT process
 * @param[in]   *pSrc 				points to the input buffer.
 * @param[in]   fftLen  			length of FFT.
 * @param[in]   *pATable 			points to the twiddle Coef A buffer.
 * @param[in]   *pBTable 			points to the twiddle Coef B buffer.
 * @param[out]  *pDst 				points to the output buffer.
 * @param[in]   modifier 	        twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
 * @return none.
 */

void arm_split_rfft_q31(
    q31_t* pSrc,
    uint32_t fftLen,
    q31_t* pATable,
    q31_t* pBTable,
    q31_t* pDst,
    uint32_t modifier)
{
	uint32_t i;                                    /* Loop Counter */
	q31_t outR, outI;                              /* Temporary variables for output */
	q31_t* pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
	q31_t CoefA1, CoefA2, CoefB1;                  /* Temporary variables for twiddle coefficients */
	q31_t* pOut1 = &pDst[2], *pOut2 = &pDst[(4u * fftLen) - 1u];
	q31_t* pIn1 = &pSrc[2], *pIn2 = &pSrc[(2u * fftLen) - 1u];

	/* Init coefficient pointers */
	pCoefA = &pATable[modifier * 2u];
	pCoefB = &pBTable[modifier * 2u];

	i = fftLen - 1u;

	while(i > 0u) {
		/*
		   outR = (pSrc[2 * i] * pATable[2 * i] - pSrc[2 * i + 1] * pATable[2 * i + 1]
		   + pSrc[2 * n - 2 * i] * pBTable[2 * i] +
		   pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);
		 */

		/* outI = (pIn[2 * i + 1] * pATable[2 * i] + pIn[2 * i] * pATable[2 * i + 1] +
		   pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
		   pIn[2 * n - 2 * i + 1] * pBTable[2 * i]); */

		CoefA1 = *pCoefA++;
		CoefA2 = *pCoefA;

		/* outR = (pSrc[2 * i] * pATable[2 * i] */
		outR = ((int32_t)(((q63_t) * pIn1 * CoefA1) >> 32));

		/* outI = pIn[2 * i] * pATable[2 * i + 1] */
		outI = ((int32_t)(((q63_t) * pIn1++ * CoefA2) >> 32));

		/* - pSrc[2 * i + 1] * pATable[2 * i + 1] */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn1 * (-CoefA2))) >> 32);

		/* (pIn[2 * i + 1] * pATable[2 * i] */
		outI =
		    (q31_t)((((q63_t) outI << 32) + ((q63_t) * pIn1++ * (CoefA1))) >> 32);

		/* pSrc[2 * n - 2 * i] * pBTable[2 * i]  */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn2 * (-CoefA2))) >> 32);
		CoefB1 = *pCoefB;

		/* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */
		outI =
		    (q31_t)((((q63_t) outI << 32) + ((q63_t) * pIn2-- * (-CoefB1))) >> 32);

		/* pSrc[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn2 * (CoefB1))) >> 32);

		/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
		outI =
		    (q31_t)((((q63_t) outI << 32) + ((q63_t) * pIn2-- * (-CoefA2))) >> 32);

		/* write output */
		*pOut1++ = (outR << 1u);
		*pOut1++ = (outI << 1u);

		/* write complex conjugate output */
		*pOut2-- = -(outI << 1u);
		*pOut2-- = (outR << 1u);

		/* update coefficient pointer */
		pCoefB = pCoefB + (modifier * 2u);
		pCoefA = pCoefA + ((modifier * 2u) - 1u);

		i--;

	}

	pDst[2u * fftLen] = pSrc[0] - pSrc[1];
	pDst[(2u * fftLen) + 1u] = 0;

	pDst[0] = pSrc[0] + pSrc[1];
	pDst[1] = 0;

}


/**
 * @brief  Core Real IFFT process
 * @param[in]   *pSrc 				points to the input buffer.
 * @param[in]   fftLen  			length of FFT.
 * @param[in]   *pATable 			points to the twiddle Coef A buffer.
 * @param[in]   *pBTable 			points to the twiddle Coef B buffer.
 * @param[out]  *pDst 				points to the output buffer.
 * @param[in]   modifier 	        twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
 * @return none.
 */

void arm_split_rifft_q31(
    q31_t* pSrc,
    uint32_t fftLen,
    q31_t* pATable,
    q31_t* pBTable,
    q31_t* pDst,
    uint32_t modifier)
{
	q31_t outR, outI;                              /* Temporary variables for output */
	q31_t* pCoefA, *pCoefB;                        /* Temporary pointers for twiddle factors */
	q31_t CoefA1, CoefA2, CoefB1;                  /* Temporary variables for twiddle coefficients */
	q31_t* pIn1 = &pSrc[0], *pIn2 = &pSrc[(2u * fftLen) + 1u];

	pCoefA = &pATable[0];
	pCoefB = &pBTable[0];

	while(fftLen > 0u) {
		/*
		   outR = (pIn[2 * i] * pATable[2 * i] + pIn[2 * i + 1] * pATable[2 * i + 1] +
		   pIn[2 * n - 2 * i] * pBTable[2 * i] -
		   pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1]);

		   outI = (pIn[2 * i + 1] * pATable[2 * i] - pIn[2 * i] * pATable[2 * i + 1] -
		   pIn[2 * n - 2 * i] * pBTable[2 * i + 1] -
		   pIn[2 * n - 2 * i + 1] * pBTable[2 * i]);

		 */
		CoefA1 = *pCoefA++;
		CoefA2 = *pCoefA;

		/* outR = (pIn[2 * i] * pATable[2 * i] */
		outR = ((int32_t)(((q63_t) * pIn1 * CoefA1) >> 32));

		/* - pIn[2 * i] * pATable[2 * i + 1] */
		outI = -((int32_t)(((q63_t) * pIn1++ * CoefA2) >> 32));

		/* pIn[2 * i + 1] * pATable[2 * i + 1] */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn1 * (CoefA2))) >> 32);

		/* pIn[2 * i + 1] * pATable[2 * i] */
		outI =
		    (q31_t)((((q63_t) outI << 32) + ((q63_t) * pIn1++ * (CoefA1))) >> 32);

		/* pIn[2 * n - 2 * i] * pBTable[2 * i] */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn2 * (CoefA2))) >> 32);

		CoefB1 = *pCoefB;

		/* pIn[2 * n - 2 * i] * pBTable[2 * i + 1] */
		outI =
		    (q31_t)((((q63_t) outI << 32) - ((q63_t) * pIn2-- * (CoefB1))) >> 32);

		/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i + 1] */
		outR =
		    (q31_t)((((q63_t) outR << 32) + ((q63_t) * pIn2 * (CoefB1))) >> 32);

		/* pIn[2 * n - 2 * i + 1] * pBTable[2 * i] */
		outI =
		    (q31_t)((((q63_t) outI << 32) + ((q63_t) * pIn2-- * (CoefA2))) >> 32);

		/* write output */
		*pDst++ = (outR << 1u);
		*pDst++ = (outI << 1u);

		/* update coefficient pointer */
		pCoefB = pCoefB + (modifier * 2u);
		pCoefA = pCoefA + ((modifier * 2u) - 1u);

		/* Decrement loop count */
		fftLen--;

	}


}
